The present invention broadly relates to air suspension systems and, more particularly, to an electronically controlled air suspension system for use in association with a stationary vehicle that adjusts the air springs of the stationary vehicle to vary the leveled height of the vehicle chassis while maintaining approximate alignment of the vehicle chassis with an artificial horizon or other predetermined datum.
The present invention finds particular application in association with the use of larger mobile vehicles, such as recreational vehicles (RVs), travel trailers and over-the-road truck trailers, for example, and will be described herein with particular reference thereto. However, it is to be understood that such vehicles are simply exemplary structures and that the present invention is capable of broader application in association with the alignment of a wide variety of structures and vehicles. Further examples of such structures and vehicles include gun platforms, military and civilian personnel transport vehicles, and ambulances.
Many larger vehicles, such as RVs, travel trailers, over-the-road truck trailers and the like, have an air suspension system for regulating the height of the vehicle chassis relative to the supporting axles, in a manner that is dependent upon the load placed in the vehicle, to adjust the height of the chassis in response to the ride conditions experienced by the vehicle. These suspension systems usually consist of a plurality of fluid suspension members, such as air springs, which support the vehicle chassis above the axles. The height of the air springs is controlled by the ingress and egress of pressurized fluid from a suitable source mounted on the vehicle, such as a compressor. One or more intervening valves are traditionally used to facilitate the ingress and egress of pressurized fluid respectively into and out of the air springs, thus adjusting the height of the air springs and correspondingly the position of the vehicle chassis relative to the vehicle axles. Such systems also enable the vehicle chassis to be maintained in an orientation substantially aligned with the axles while the vehicle is stationary. This is accomplished by individually regulating the heights of the air springs that support the vehicle chassis on the axles. One disadvantage of such systems, though, is that the chassis can only be positioned relative to the axles. So, if the axles are disposed in an undesirable orientation, the chassis, though level with the axles, will also be disposed in an undesirable orientation.
As an alternative, many of these vehicles, such as RVs, will also use a plurality of hydraulic jacks, which are lowered in order to level the floor of the RV when in a stationary, parked condition. However, in certain situations, the use of hydraulic jacks is not permitted, such as when the RV is parked on an asphalt parking lot since the jacks could damage the asphalt. Thus, leveling of the vehicle cannot be accomplished under these circumstances. Another disadvantage is the cost associated with these systems, as few of the standard components of the vehicle are utilized therein. That is, the hydraulic jacks, the control valves, the hydraulic lines, the electronic control unit, and the user interface, as well as other components, must be installed on the vehicle, over and above all of the standard components that are already installed. Thus, these extra components increase the cost of the vehicle in order to obtain the leveling feature.
Also, some RVs may use the existing suspension air springs to adjust the floor height and to level the floor by the use of mercury switches, or other controls which will raise and lower certain of the air springs to regulate the height of the floor with respect to the vehicle axles until a level condition is reached. Some examples of such fluid actuated leveling systems for trailers, RVs, etc., are shown in U.S. Pat. Nos. 5,228,704, 5,465,209, 5,180,024, 5,499,845, 6,431,557, and 6,428,026. However, it will be appreciated that these systems may be useful in situations where weight distribution changes in a parked or otherwise stationary vehicle. However, these systems remain ineffective for leveling a vehicle chassis when the axles of the vehicle are not themselves in a level orientation.
The above-listed patents disclose numerous leveling and suspension control systems for air springs in vehicles, some of which are operational while the vehicle is moving, while others are actuated when the vehicle is stationary. Most of these systems use the air springs to regulate the height of the vehicle chassis with respect to the axles or the wheel supporting structure in order to achieve a level condition. Also, many of these systems require separate control systems which are in addition to the existing suspension components and pneumatic ride control system of the vehicle.
Another issue that can arise with known leveling and suspension control systems involves the leveled height at which the sprung mass of the vehicle is stationed above the ground. Once a the chassis or body of a vehicle has been leveled, known leveling and suspension control systems are not typically provided with the capability to alter the leveled height of the chassis or body while maintaining the leveled orientation of the same. That is, known systems are normally unable to raise or lower the sprung mass of the vehicle without undesirably altering the leveled condition of the vehicle.
As an example, where the suspension system of an RV has been adjusted such that the sprung mass of the RV is in a leveled condition, it may be desirable to raise or lower the leveled height of the sprung mass of the RV. Such a situation might exist where the folding stairs of the RV will not fully extend because the body of the RV is stationed too low to the ground. Alternately, a situation might exist in which the folding stairs of the RV are spaced too far from the ground even when fully extended. In either case, it may be desirable to raise or lower the body of the RV.
To adjust the height of a leveled body or chassis of a vehicle that is outfitted with a known leveling or suspension control system, such as may be provided on an existing RV, for example, an operator could individually adjust each of the suspension members of the suspension system in an attempt to achieve a leveled condition at the desired or target height. Due to the manual operation of such known systems, however, further adjustment of the suspension system to re-level the body or chassis of the vehicle to a leveled orientation might be required. Unfortunately, this further adjustment may undesirably alter the leveled height from the previously desired or targeted height. As such, adjusting the height of known leveling and suspension control systems can be an iterative process that is challenging and somewhat time consuming.
For at least these reasons, it is considered desirable to develop an air suspension system that overcomes these as well as other disadvantages.